DE 10 2004 015 278 A1 shows a differential gear for the driving of two coaxial, rotating shafts in which the gear housing coaxial to the shafts is driven in a rotating manner by, for example, a toothed belt. The differential gear is a spur gear transmission.
A spur gear differential or transmission is a transmission like a kind of planetary gearing in which the compensation elements engaging with each other via teeth are gearwheels with spur teeth.
The spur gear differential of the class-forming type is provided with a first sun and a second sun. A first set of planet gears is associated with the first sun and a second set of planet gears is associated with the second sun, wherein they are all spur gears. The first set of planet gears meshes with the second set of planet gears.
In DE 10 2006 019 131 B4, a distributor gear with differential is described in which the differential is a bevel gear differential and the downstream active axle gear is a planetary gear with a first sun and a second sun. A first set of planet gears is associated with the first sun and a second set of planet gears is associated with the second sun. The number of teeth of the first sun is equal to the number of the second sun. An active-yaw function of the branches is achieved by the effective diameter ratio of the first teeth to the second teeth. Initially, a different tooth count is proposed as the simple average that is, however, actually complicated to estimate. Alternatively, the same tooth count of the two sets of teeth is also proposed, wherein then by means of a profile displacement, the necessary transmission ratio is provided between the second gearwheel that is coupled with the side shaft and the first gearwheel coupled with the differential housing.
The profile displacement is a measure known to someone skilled in the art by which teeth for various operating conditions can be produced, for example, with the same tools [Dr. S. Fronius, Chapter 6, “Design of driving elements,” Verlag Technik Berlin, 1982].
The tooth profile of a spur gear is initially unambiguously defined by the reference profile and its position relative to the reference circle. The reference circle is a mathematical parameter and a circle that is perpendicular to the axis of the gearwheel and whose circumference is the product from the tooth count and the reference circle pitch. The reference circle pitch is a circular are lying on the reference circle from one tooth center to another tooth center and is a multiple of π, so that the reference circle D0 is finally produced from the product from the modulus and the tooth count. The modulus m is the ratio of the pitch ρ to π, m=ρ/π. In the technical world, the reference circle D0 is also named the base circle or generating pitch circle.
Pitch circles are the imaginary circles of the gearwheels about the axis of each gearwheel, wherein these pitch circles contact at the pitch point and roll on each other there, without sliding relative to each other [see also K. Zirpke, “Gearwheels,” VEB Fachbuchverlag Leipzig, 11th edition]. In other words, in this case, the two tooth flanks of the gearwheels in meshing contact transfer the rotational movement at a constant transmission ratio when their shared contact normal always goes through the pitch point. The pitch circles of such meshed parts of gearwheels are the reference circles (O-wheels).
The pitch-circle diameters of the paired wheels (diameters of the working pitch circles) could alternatively by larger or smaller than their reference-circle diameters (V-wheels). A fundamental quantity for defining the teeth is thus the radial distance of the profile reference line from the pitch point lying on the reference circle.
Therefore, the already mentioned O-wheels and V-wheels are distinguished according to the position of the profile reference line of the reference profile to the reference circle. For 0-wheels, the profile reference line forms a tangent to the reference circle. For V-wheels, the profile reference line does not form a tangent to the reference circle, but instead lies outside of the reference circle in the radial direction or intersects it at two points.
The radial distance (in millimeters) of the profile center line from the pitch point is designated as the profile displacement. The numerical value of the profile displacement for modulus 1 is designated as the profile displacement factor x and is given from the ratio of the profile displacement to the modulus. In other words, the quantity of the profile displacement is expressed with the factor x in fractions of the modulus (xm), the profile displacement divided by the modulus. For a positive profile displacement, the profile reference line lies outside of the reference circle. For a negative profile displacement, the profile reference line intersects the reference circle.